The present invention relates to the treatment of wastewater septic systems with aerobic and/or anaerobic alkane-utilizing bacteria.
Septic systems provide on-site wastewater management for individual residences and other establishments. Typical septic systems may include at least some of the following components: septic tanks, grease and oil interceptor tanks, Imhoff tanks, drain or leach fields, disposal beds and pits, intermittent sand filters, recirculating granular-medium filters, shallow-trench sand-filled pressure-dosed disposal fields, mound systems, complete recycle units and graywater systems.
Septic systems are often used for residential wastewater treatment. As more people move to rural and suburban areas not serviced by municipal or community sanitary sewers, the solution for the treatment of household waste continues to be on-site sewage disposal. Wastewater may also be generated at housing units, public facilities and commercial establishments such as restaurants. Waste includes fats and oils, grease, sludge, human waste, food/garbage disposal waste, paper products and laundry effluent.
Conventional wastewater treatment processes are microbiologically mediated. Naturally occurring anaerobic bacteria breakdown and digest the solid waste that falls to the bottom of the septic tank. The microbial processes acting on the solids in the tank may reduce the solids to gases and fine particles. These small solid particles, as well as the oils and greases, float on the surface of the tank and form a scum layer. In the process of floating to the top of the tank, some of the small solid particles, oils, and greases are forced out by the flow of water into the outlet baffle leading into the drainfield. With time, the buildup of small solid particles, oils and greases, and soaps, can cause serious problems in the drainfield.
During normal operation, septic systems fail due to clogging. For example, clogging can occur in septic tanks, grease and oil interceptor tanks and drainfields, including the piping of such systems. The clogging may be caused by, e.g., biomass buildup or grease buildup. Clogged drainfields are a common and expensive problem facing septic system owners.
In addition to clogging problems, decomposing wastes in conventional septic tanks may produce toxic gases such as hydrogen sulfide under anaerobic conditions. In addition to being a potential health hazard, hydrogen sulfide can be corrosive to tanks and piping networks. Another disadvantage of conventional septic systems is that household chemicals flushed down a toilet or sink can contaminate a drainfield and the subsurface soils and groundwater, resulting in a wide spread contaminant plume and significant liability for the property owner. Contaminated drainfields are very expensive to remediate using conventional treatment technologies.
Industrial wastewater and municipal wastewater have been conventionally treated by the introduction of air or oxygen bubbles. The addition of micro bubbles of air or oxygen provides enhanced aerobic treatment of industrial and municipal wastewater to lower biological oxygen demand (BOD), total dissolved solids (TDS) and total organic carbon (TOC).
The bioremediation of various pollutants such as chlorinated solvents and other types of pollutants using butane-utilizing bacterial is disclosed in U.S. Pat. Nos. 5,888,396, 6,051,130, 6,110,372, 6,156,203, 6,210,579, 6,245,235 and 6,488,850, which are incorporated herein by reference.
The present invention provides methods and apparatus for treatment of septic systems with alkanes. In a preferred embodiment, butane, having the highest solubility of all the alkanes, can be used to control, for example, septic system BOD, TOC and TDS through enhanced growth of aerobic and/or anaerobic bacteria and other microorganisms that oxidize (or reduce) dissolved organic matter and sludge effluents. For example, sludge and BOD of septic system wastestreams may be significantly decreased. In addition, pollutants found in the septic system wastewater may be remediated by the alkane-utilizing bacteria.
An embodiment of the present invention provides enhanced aerobic treatment of wastewater effluent from houses, housing units, public facilities and commercial establishments such as restaurants by introducing alkane(s) and oxygen-containing gas into a treatment vessel, such as a septic tank or other portion of a septic system, thereby providing an aerobic bioreactor. The creation of an aerobic environment avoids the generation of hydrogen sulfide, and can extend the life of septic tanks and piping systems. In addition, the alkane(s) and oxygen-containing gas may be injected into a drainfield to improve field performance, or into oil and grease interceptor tanks to reduce the solids content.
Another embodiment of the present invention provides enhanced anaerobic treatment of septic system wastewater by introducing an alkane(s) into a treatment vessel to stimulate the growth of anaerobic bacteria to thereby provide an anaerobic bioreactor.
A further embodiment of the present invention is to use alkanes, e.g., methane, ethane, propane and butane, to effectively degrade compounds such as pollutants typically found in small on-site wastewater treatment systems. Additionally, butane with or without air (oxygen) may be used to remediate contaminated leach fields.
An aspect of the present invention is to provide a method of treating septic system wastewater comprising introducing at least one alkane into wastewater contained in the septic system.
Another aspect of the present invention is to provide a method of treating material contained in septic system wastewater, the method comprising stimulating growth of alkane-utilizing bacteria, and allowing the alkane-utilizing bacterial to degrade at least a portion of the septic system wastewater material.
A further aspect of the present invention is to provide an apparatus for treating septic system wastewater comprising means for introducing at least one alkane into wastewater contained in the septic system.
Another aspect of the present invention is to provide an apparatus for treating septic system wastewater comprising a septic system wastewater containment vessel, and at least one alkane injector in flow communication with the septic system wastewater containment vessel.
These and other aspects of the present invention will be more apparent from the following description.